The present invention relates to compositions and methods for preventing or treating dental hypersensitivity.
The three mineralized tissues of teeth are enamel, cementum and dentine. In human teeth, enamel covers the crown dentine whereas cementum covers the root dentine. In turn, the dentine encloses the pulp of the tooth which provides the dentine with vascular and neural support. Unlike enamel and cementum, the dentine is transversed by numerous tubules. The tubule walls are comprised of the calcified matrix of the dentine and the tubule space is filled with fluid (dentinal fluid) derived from pulp tissue fluid and serum. The matrix mineral is comprised mainly of the calcium phosphate salt, hydroxyapatite, which is poorly soluble at neutral and alkaline pH, and progressively more soluble as the pH becomes progressively more acidic.
Because of their rigid walls, the fluid that fills the narrow dentinal tubules enables cold, tactile, evaporative and osmotic stimuli to be transmitted through the dentine to the pulp in the form of fluid movement. This movement of dentinal fluid is sensed as sharp pain of short duration. This pain is elicited when the odontoblasts that protrude into the pulpal ends of the tubules are disturbed and as a result, the mechano-receptors of the pulpal nerve fibers attached thereto are stimulated. The neural response is usually referred to as dentinal pain and the involved dentine as hypersensitive dentine.
Dentinal hypersensitivity results when protective enamel or cementum covering dentine is lost. Cementum is easier to breach than enamel, because cementum is thinner and more easily eroded by acids. However, breach of cementum cannot happen until there is gingival recession and exposure of the root surface to the oral milieu. Individuals with breached cementum and suffering with dentinal hypersensitivity often experience pain when the exposed area of the tooth comes into contact with cold air or hot and cold liquids or foods that are sweet or acidic or is touched with a metal object.
One way that loss of cementum occurs (and the same is true of enamel) is by the process of dental caries. Acids are produced as end-products of the bacterial degradation of fermentable carbohydrate and these acids dissolve hydroxyapatite, which, like dentine and enamel, is the main calcium phosphate mineral that comprises most of the mineral of the cementum. Another source is acidic foods which, if ingested frequently and for prolonged periods of time, will cause tooth demineralization. These include fruit juices and many beverages, both alcoholic and non-alcoholic. Other acidic agents leading to chemical erosion include various oral personal care products. Amongst these are many of the commercially available mouthwashes and some toothpastes. Abrasive toothpastes and vigorous brushing can aid the erosion process. Another way in which dentinal tubules lose their protective cementum and enamel coverings is through procedures performed by the dentist or hygienist in the dental office. This includes cavity and crown preparation of teeth for fillings and other restorations. It also includes cementum removal during scaling and root planing by the periodontist or dental hygienist.
Many attempts have been made with limited success to plug exposed dentinal tubules and to thereby reduce or stop the ability of stimuli to reach the pulp and cause pain. Materials either singly or in combination have been tried to produce an effective plug. Blockage of the tubules through the formation of a calcium phosphate precipitate is a common approach. This includes the mixing of a soluble calcium salt with a soluble phosphate salt and immediately applying the combination to the open tubules. Alternatively, application of one salt before the other to try to get a precipitate to form within tubules is also used.
Substances other than calcium phosphate have also been utilized. For example, U.S. Pat. No. 3,683,006 to Hodosh describes using potassium, lithium or sodium nitrate. Another example is calcium oxalate particles of small and large size. Application of a protein denaturing agent, such as an alcohol, a surfactant, or a chaotropic salt, can also plug an exposed dentinal tubule since there is protein material within the dentinal tubules and denaturation can sometimes result in partial or complete tubule plugging. Still another but more drastic approach is to place a dental restoration in the affected area or cover the area with an adhesive material. For example, U.S. Pat. No. 5,139,768 to Friedman describes using a varnish containing strontium salt in a sustained hydrophobic polymer. Adherence without leakage of fluid from the tubules is not always easy to accomplish because adherence to a wet surface is difficult to achieve considering that the continual outward flow or leakage of dentinal fluid from the tubules while a filling or adhesive is setting is hard to stop.
Attempts to treat tooth sensitivity other than by plugging have involved depolarization of the nerve fiber membranes essential for nerve impulse transmission. Potassium salts, especially potassium nitrate, have been largely used for this purpose. For example, U.S. Pat. Nos. 4,751,072 and 4,631,185 to Kim describe using potassium bicarbonate and potassium chloride.
Thus, there remains acute need in the art for compositions and methods for blocking exposed dentinal tubules to treat dentinal hypersensitivity.
There is a further need in the art to identify compositions and methods that can achieve intrinsic blockage of dentinal tubules, e.g., by taking advantage of the presence of calcium and phosphate ions in dentinal fluid, which potentiates their ability to precipitate as a calcium phosphate salt and achieve tubule blockage.
The present invention advantageously provides such compositions and methods.
The present invention advantageously provides an oral composition comprising a guanidinium alkaline salt and a calcium salt and an orally acceptable carrier, wherein the pH of the composition ranges from about 7.5 to about 9.5, and the calcium salt is poorly soluble in water. In a more specific embodiment, the oral composition consists essentially of the guanidinium alkaline salt and poorly soluble calcium salt with an orally acceptable carrier. In yet a further embodiment, the oral composition substantially lacks any phytates. Preferably, the guanidinium is arginine and the calcium salt is calcium carbonate.
The invention further provides a powder composition comprising, or more particularly consisting essentially of, an arginine salt (or equivalent guanidinium salt) and calcium carbonate (or an equivalent poorly soluble calcium salt). Such a powder composition, when in contact with a calcium phosphate solution or slurry, or a body fluid (e.g., dentinal fluid, saliva, or pulpal fluid), body cells, or body tissues (e.g., dental pulp), yields a pH ranging from about 7.5 to about 9.5. Preferably, the powder composition lacks phytates.
In a further aspect, the invention provides a pulpal calcification filling comprising, or more particularly consisting essentially of, an arginine salt (or an equivalent guanidinium salt) and calcium carbonate (or an equivalent poorly soluble calcium salt) and a filling carrier, wherein the pH of the composition ranges from about 7.5 to about 9.5.
The invention further provides methods for treating or preventing dentinal sensitivity, plugging tubules, treating a carious lesion, calcifying an exposed tooth pulp, and calcifying the base or all of a pit or fissure in a tooth. The methods comprise administering a composition comprising, or more particularly consisting essentially of, an arginine (or equivalent guanidinium) salt and calcium carbonate (or an equivalent poorly soluble calcium salt), wherein a pH of the composition ranges from about 7.5 to about 9.5, to the affected area.
Thus, it is an object of the invention to provide a composition suitable to calcify dental lesions.
The invention has as a further object a composition for reducing dentinal sensitivity.
Another object of the invention is to provide methods for calcifying dental lesions, including dentinal tubules, exposed tooth pulp, carious lesions, and pits or fissures.
These and other objects of the invention have been achieved as further elaborated in the accompanying Drawings, Detailed Description of the Invention, and Examples.